Regression in 6.2.3: Semaphore Disposed Exception thrown in AsyncConsumerWorkService

[ashneilson]

Refer to the original issue for context #1014

Problem

When under load, stopping the AsyncConsumerWorkService can result in System.ObjectDisposedException being thrown due to a Disposed _limiter.

The Discarded Tasks HandleConcurrent started in LoopWithConcurrency may still be running after the finally block disposes of the _limiter Semaphore.

rabbitmq-dotnet-client/projects/RabbitMQ.Client/client/impl/AsyncConsumerWorkService.cs

Lines 125 to 151 in 4628927

	private async Task LoopWithConcurrency(CancellationToken cancellationToken)
	{
	try
	{
	while (await _channel.Reader.WaitToReadAsync(cancellationToken).ConfigureAwait(false))
	{
	while (_channel.Reader.TryRead(out Work work))
	{
	// Do a quick synchronous check before we resort to async/await with the state-machine overhead.
	if (!_limiter.Wait(0))
	{
	await _limiter.WaitAsync(cancellationToken).ConfigureAwait(false);
	}
	_ = HandleConcurrent(work, _model, _limiter);
	}
	}
	}
	catch (OperationCanceledException)
	{
	// ignored
	}
	finally
	{
	_limiter?.Dispose();
	}
	}

When the HandleConcurrent Tasks attempt to Release the Semaphore, the System.ObjectDisposedException is thrown.

rabbitmq-dotnet-client/projects/RabbitMQ.Client/client/impl/AsyncConsumerWorkService.cs

Lines 181 to 186 in 4628927

	}
	finally
	{
	work.PostExecute();
	limiter.Release();
	}

The issue doesn't occur in 6.2.2 but does in 6.2.3. It appears the PR #1113 might be the culprit.

Recommended Fix

• Release a patch version (possibly 6.2.4) with PR fix model shutdown event handler corner case #1113 reverted
• Release a patch version (possibly 6.2.4) with a fix applied to the 6.x branch

I'd be more than happy to submit a PR with a fix if that's the desired approach.

[michaelklishin]

@ashneilson please submit a PR if you understand what needs to be done (not just a revert).

[ashneilson]

@michaelklishin Thanks for the quick reply! PR submitted as requested

[lukebakken]

Thanks I'll get to this today.

[lukebakken]

Fixed by #1154 and will ship in 6.2.4.